Gonadotropins in the Male
This chapter describes both luteinizing hormone (LH) and follicle-stimulating hormone because these two gonadotropins have many similarities, including a common hypophysiotrophic neurohormone and sometimes a common cell of origin in the adenohypophysis. In addition to species differences in the incidence of bihormonal gonadotrophs, the intensity of gonadotropin secretion may influence the proportion of bihormonal cells. Hormones that are related to the pituitary gonadotropins include human chorionic gonadotropin and pregnant mare serum gonadotropin. In contrast, serum inhibin increased as male monkeys attained puberty. Simplified diagram illustrating regulation of gonadotropin secretion in the male. Monohormonal and bihormonal gonadotroph cells in the adenohypophysis are depicted with different shading. Circulating LH secreted into blood by the gonadotroph cells of the adenohypophysis binds to cell-surface receptors on the interstitial cells of the testis. There are multiple isoforms of each hormone existing in the tissue of the adenohypophysis, and some of these isoforms may be secreted into the blood.